JPH0480627A - Optical detector - Google Patents

Abstract

PURPOSE:To make it possible to check at all times whether a pair of ultraviolet detection discharge tubes operate normally or not, by a method wherein the numbers of pulses accompanying the respective discharges of the ultraviolet detection discharge tubes are compared with each other at each prescribed time. CONSTITUTION:The respective discharge pulses of ultraviolet detection discharge tubes 1a and 1b in a pair are inputted onto the addition side and the subtraction side of an incremental/decremental counter 20 of a fault detecting element 15 and subjected to comparison by addition and subtraction for a prescribed time, e.g. 10 seconds. The discharge tubes are judged to be normal when a comparison value thus obtained is a prescribed value or below, and the counter 20 is reset, counting being made again. When the comparison value obtained for 10 seconds exceeds the prescribed value, either one of the discharge tubes 1a and 1b is judged to be faulty and a fault detection signal is outputted. All the discharge pulses of the discharge tubes 1a and 1b are inputted to an FF circuit 26. When the discharge tubes 1a and 1b are normal, a dark discharge is once generated at least within a certain time. When no discharge pulse is generated within a long set time, e.g. one hour, both of the discharge tubes 1a and 1b are judged to be faulty and the fault signal is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a light detection device such as a fire detector or a burner ignition detector. More specifically, an ultraviolet detection discharge tube starts discharging in response to ultraviolet light emitted from a flame, so by detecting the discharge current of this discharge tube, it is possible to detect a fire or ignition of a burner.

``Prior Art'' An ultraviolet detection discharge tube starts discharging when ultraviolet rays are incident on its cathode surface, but although it is normal, it produces an undesirable discharge called dark discharge, in which it discharges even when no ultraviolet rays are input. This dark discharge has the characteristics that the occurrence interval is random and it is sufficiently long in terms of time. A conventional photodetecting device that prevents malfunctions caused by dark discharge is shown in FIG.

In this circuit, an operating voltage is supplied to an ultraviolet detection discharge tube (1) from a power supply circuit (2) consisting of a booster circuit. The ultraviolet detection discharge tube (1) discharges at a frequency approximately proportional to the intensity of the incident ultraviolet light, and the pulses generated in the resistor (7) during discharge as shown in Fig. 7(a) trigger the retrigger multivibrator (3). ) and is also supplied to the counting input terminal of the counter (4).

Then, the output shown in (b) is obtained from the retrigger multivibrator (3) and is supplied to the reset terminal of the counter (4), and the falling edge becomes a reset signal. The output pulse from the ultraviolet detection discharge tube (1) is passed through a counter (
4), and when the value selected by the selection switch circuit (5) is reached, a detection output is issued from the output circuit (6) as shown in (d).

Here, the dark discharge occurs sporadically, and the discharge interval (To
) is the pulse of retrigger multivibrator (3) +1
Since it is sufficiently longer than @T (for example, 2 seconds), it is reset at the fall of the output in (b) and is not integrated by the counter (4).

Next, if the discharge interval (To) of the ultraviolet detection discharge tube (1) by ultraviolet rays is shorter than the pulse width (To), the falling edge of the retrigger multivibrator (3) is sequentially extended and the counter is not reset. The output pulses of (4) are sequentially integrated. When the set value is reached, an output is generated from the output circuit (6) as shown in (d). Note that the pulse width (T□) is set longer than the discharge interval for weak ultraviolet rays. Moreover, if the ultraviolet rays are strong, the discharge interval will naturally be shorter, so the cumulative time until the counter (4) reaches a certain number will be shorter, and the operating time will be shorter.

"Problems to be Solved by the Invention" The conventional devices described above are configured so that they do not malfunction even if the ultraviolet detection discharge tube is subjected to dark discharge, but if the ultraviolet detection discharge tube should fail, There was a problem that the device no longer worked correctly. The first possible cause of failure is that since the ultraviolet detection discharge tube is made of glass, the glass tube is damaged by external pressure, and even if ultraviolet rays are incident, no discharge occurs and no signal pulse is output. In such a case, the device will not work and will not issue an alarm in the event of a fire. Another case is a so-called self-discharge, in which a malfunctioning ultraviolet detection discharge tube continuously discharges and outputs signal pulses even though no ultraviolet rays are incident on it. In such a case, the device will malfunction and issue a false alarm even though there is no fire.

In addition, as a malfunction prevention circuit due to dark discharge or self-discharge,
There is a study that states that a normal discharge occurs only when a pair of ultraviolet detection discharge tubes discharge alternately with a phase difference of 180 degrees (Japanese Patent Publication No. 39874/1983).

However, even with this, there was a problem that it was not possible to distinguish whether the ultraviolet detection discharge tube did not discharge due to a failure or whether it did not discharge because ultraviolet light was not incident.The present invention always checks whether the ultraviolet detection discharge tube is operating normally. The purpose is to get what you want to check.

"Means for Solving the Problems" The present invention provides a photodetection device in which a pair of ultraviolet detection discharge tubes are shifted by half a cycle and discharged alternately, in which the number of pulses accompanying the discharge of each ultraviolet detection discharge tube is The first signal is compared at regular intervals and is output when the difference between the two is greater than a predetermined value.
The system is equipped with a failure detection section.

"Operation" Out of a pair of ultraviolet detection discharge tubes, the discharge pulse of one ultraviolet detection discharge tube is input to the addition side of the counter of the failure detection section, and the discharge pulse of the other ultraviolet detection discharge tube is input to the same counter. Input on the subtraction side. Then, addition and subtraction are compared for a certain period of time, for example, 10 seconds. If this comparison value is less than or equal to a predetermined value, it is considered normal, and the counter is reset and counted again. If the comparison value for 10 seconds exceeds a certain value, it is determined that one of the two ultraviolet detection discharge tubes is at fault, and a failure detection signal is output. In addition to the second counter, all discharge pulses from the two ultraviolet detection discharge tubes are input to a flip-flop circuit. If the ultraviolet detection discharge tube is normal, dark discharge will occur at least once within a certain period of time. However, if there is no discharge pulse within the set long time 1, for example, 1 hour, 2
It was determined that both of the ultraviolet detection discharge tubes were malfunctioning.
Outputs a failure detection signal.

"Example" Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, (la) and (lb) are ultraviolet detection discharge tubes having the same performance as possible. These first and second ultraviolet detection discharge tubes (la) (lb) each have a resistor (7
a) It is coupled to the power supply circuit (8a) (8b) via (7b).

These power supply circuits (8a) (8b) supply low voltage DC voltage.

It is for boosting the voltage to 300~400V, and it consists of transistors (9a) (9b), transformer (10a) (10b).
), rectifier diodes (lla) (llb), and smoothing capacitors (12a) (12b).

As shown in FIGS. 2(a) and 2(b), an oscillator (13) for applying oscillation pulses shifted by half a period from each other is coupled to the bases of the transistors (9a) and (9b).

On the output side of the ultraviolet detection discharge tube (la) (lb).

A fire signal detection section (14) and a failure detection section (15) are coupled.

Of these, the fire signal detection section (14) includes a first OR gate (16) and a first retrigger multivibrator (3).
, a counter (4), a selection switch circuit (5), an output circuit (6) consisting of a second multivibrator, and a fire detection signal output terminal (17), basically the input of the circuit shown in Figure 6. It combines an AND gate on the side. The failure detection unit (15) also includes a first failure detection unit (18) for detecting a failure in either one of the two ultraviolet detection discharge tubes (la) (lb), and a first failure detection unit (18) for detecting a failure in either one of the two ultraviolet detection discharge tubes (la) (lb). A second fault detection unit (1
9). Among these, the first failure detection unit (18)
is an up/down counter (20) and a first timer (2
1). Further, the second failure detection section (19) includes a flip-flop circuit (22), a second timer (23), and a Nant gate (24). In addition, the failure detection section (
15) includes a second OR gate (25), a second flip-flop circuit (26), and a failure detection signal output terminal (2
7). (28) is a reset signal terminal.

The operation of the above configuration will be explained. The DC low voltage power supply (2) is chopped with transistors (9a) (9b), boosted with transformers (10a) (10b), and rectified and smoothed with diodes (lla) (llb) and capacitors (12a) (12b). Figure 2 (c)
As shown in (d), ultraviolet detection discharge tube (la) (lb
) is boosted to the required operating voltage of 300 to 400 V and applied.

More specifically, the transistors (9a) (9b)
The oscillation pulses input to the base of the oscillation pulses are very thin pulses with a duty ratio of, for example, 1:1000, and their oscillation periods are shifted from each other by half a cycle.

For example, as shown in Figure 2 (a) and (b), 10m5ec
The pulse width is assumed to be 5111 seconds apart from each other, and the pulse width is 10 μsec.

The oscillation pulses shown in (a) and (b) cause the transistor (
9a) 10μse between collector and emitter of (9b)
The current flows through the primary side of the transformer (LOA) (10b).

A voltage proportional to the winding ratio is generated on the secondary side of these transformers (10a) (10b), and the voltage is passed through the rectifier diodes (lla) (llb) and then the smoothing capacitor (llb).
12a) (12b).

Capacitors (12a) as shown in (c) and (d) (
12b) is the voltage across the ultraviolet detection discharge tube (la) (
lb). Ultraviolet detection discharge tube (LA) (L
The applied voltage in b) is
) is not discharged, it will gradually drop due to leakage current from the capacitor, etc., but it will not drop below the operating voltage of the ultraviolet detection discharge tube (la) (lb) until the first charge (after 10 msec). .

Here, when ultraviolet rays are incident on the ultraviolet detection discharge tubes (la) (lb), discharge occurs and a discharge current flows. The charge had been stored in the capacitors (12a) (12b), and the charge is consumed by discharge, and the voltage applied to the ultraviolet detection discharge tube (la) (lb) drops to near zero volts. - The reduced voltage will not recover until the next charge.

When the ultraviolet detection discharge tube (la) (lb) discharges, it emits ultraviolet light, and the emission time is equal to the discharge time. The discharge current flows through the resistors (7a) (7b), and the discharge time is determined by the capacitance of the capacitors (12a) (12b) and the impedance of the discharge path. For example, capacitors (12a) (12b) are 47pF, resistor (7a)
When (7b) is set to IOKΩ, its time constant is 0.
The time is 47 μsec.

The discharge current waveforms appearing at both ends of the resistors (7a) and (7b) are shown in (e) and (f), and the discharge time, that is, the light emission time of the ultraviolet detection discharge tube (la) (lb), is the same as that of the ultraviolet detection discharge tube (la). (1b) Charging cycle (1
Since it is sufficiently shorter than the half cycle (5 msec) of 0 msec), the ultraviolet detection discharge tubes (la) and (1b) do not cause mutual interference due to their own light emission.

Here, the fire signal detection section (14) performs the following operation in substantially the same manner as the conventional example shown in FIG.

Figure 3 (g) (
A pulse like h) is supplied to the retrigger multivibrator (3) via the first OR game)-(16), and a pulse like (i) is supplied to the counting input terminal of the counter (4). Ru. Then, the output shown in (r) is obtained from the retrigger multivibrator (3) and is supplied to the reset terminal of the counter (4), and the falling edge becomes a reset signal. The ultraviolet detection discharge tube (1a) (lb
) is integrated by the counter (4), and when it reaches the value selected by the 1 selection switch circuit (5), the output pulses from the second multivibrator output circuit (6) are integrated by the counter (4).
) The detection output is emitted as follows.

Here, the dark discharge occurs sporadically, and the discharge interval (T,
) is the pulse intensity T of the retrigger multivibrator (3)
1 (for example, 2 seconds), it is reset at the fall of the output of (r) and is not integrated by the counter (4), so that no fire detection signal is output.

Next, the operation of the failure detection section (15) of the ultraviolet detection discharge tubes (la) (lb) will be explained. There are the following two failure modes of the ultraviolet detection discharge tube.

(1) Failure due to leakage of filled gas (both failures due to damage due to external pressure) In this case, the ultraviolet detection discharge tube will not discharge even if ultraviolet rays are incident. It also does not cause dark discharge.

(2) Failure due to self-discharge (failure of either one) Ultraviolet detection discharge tubes are sensors that generate discharge when ultraviolet rays are incident on them, but sometimes they also cause discharge due to light other than ultraviolet rays, such as visible light.

Further, even if no light is incident at all, discharge may occur continuously.

First, the second failure detection unit (19) for detecting failure mode (1) failure due to leakage of sealed gas will be described. A state in which the ultraviolet detection discharge tube does not operate at all due to a leak of filled gas is the same as a state in which there is no ultraviolet light in the surrounding area, and it is difficult to distinguish between the two.

However, dark discharge occurs even when there is no ultraviolet light in the surrounding area, but it does not occur when there is a failure. Focusing on this point, dark discharge is monitored for a certain period of time, and if there is no dark discharge after a certain period of time, it is determined that there is a failure and a failure signal is output.

This will be explained in more detail with reference to the time chart shown in FIG.

Signal pulses (g) and (h) due to dark discharge from the ultraviolet detection discharge tubes (la) and (lb) are the first OR gate (16
) is added and becomes (i). The added signal pulse is connected to the set input of the flip-flop circuit (22) to set it. On the other hand, timer (23)
is set to one hour in the embodiment, and outputs a reset signal for one second every hour as shown in (j). The output Q(k) of the flip-flop circuit (22) and the timer (j
) are respectively input to the Nantes gate (24),
The output is as shown in (Q).

If there is a signal pulse even once in a certain period of time (one hour in the embodiment), the output of the Nandt gate (24) does not change.

Next, when both the ultraviolet detection discharge tubes (la) and (lb) are damaged, the flip-flop circuit (22) is not set, and the output of the Nant gate (24) changes after a certain period of time, generating a failure signal. This situation is shown in (q).

Next, the part for detecting failure mode (2), a failure due to self-discharge, will be explained. This is the first fault detection section (1
8) is detected. The state in which signal pulses are output from the ultraviolet detection discharge tube due to self-discharge is the same as when ultraviolet light is present in the surroundings, and it is difficult to distinguish between the two. Although it cannot be determined with one tube, two ultraviolet detection discharge tubes are used,
Failure can be detected by monitoring the difference in the number of signal pulses from both ultraviolet detection discharge tubes. That is, when one ultraviolet detection discharge tube causes self-discharge, if the other ultraviolet detection discharge tube is normal, there will be a difference in signal output between the two.

Further, even if one ultraviolet detection discharge tube is normal and the other ultraviolet detection discharge tube has leaked gas and does not output any signal at all, a difference will similarly occur between the two signal outputs.

This will be explained in more detail with reference to the time chart shown in FIG.

The signal pulse (g) from the UV detection discharge tube (1a) is connected to the UP count input of the up/down counter (20), and the signal pulse (h) from the UV detection discharge tube (1b) is connected to the UP count input of the up/down counter (20). ) is connected to the DOWN count input. This counter (20) is a decimal counter in the embodiment, and is initially set to an intermediate value of "5" by a preset input. A counter (2
0) repeats UP count input and DOIIN count, and if the number of signal pulses from both ultraviolet detection discharge tubes (la) and (lb) is almost the same, it changes only by ±1 to 2 counts around "5". This situation is shown in (n).

In addition, the timer (21) is used to forcibly preset the counter (20) to ii 5 u at regular intervals, and this is used to forcibly preset the counter (20) to ii 5 u. This is to prevent the difference from increasing eventually and outputting a failure signal. In the example, 10
The counter is preset to "5" every second.

This situation is shown in (m).

Now, if one of the ultraviolet detection discharge tubes breaks down (in Figure 5, it is assumed that the ultraviolet detection discharge tube (1a) has caused self-discharge), the signals of both will be unbalanced, and in one case, the UP count will increase. Eventually, an overflow occurs and a carry output is output. This situation is shown in (p). On the other hand, when the ultraviolet detection discharge tube (1b) causes self-discharge, the DOWN count continues until it reaches zero and outputs a borrow output.

These carry outputs, borrow outputs, and the output of the Nant gate (24) are all input to an OR gate (25) and added to set a flip-flop circuit (26). This situation is shown in (9). Since the output Ω of the flip-flop circuit (26) is connected to the disable of the output circuit (6) of the fire detection signal, when a failure signal is output, the fire detection signal is No output.

Furthermore, the failure signal continues to be output until a reset signal from the outside (28) is input.

"Effects of the Invention" Since the present invention is configured as described above, it has the following effects.

(1) By using two ultraviolet detection discharge tubes, they can monitor each other's signals, and if one breaks down, this can be reliably detected.

(2) Utilizing the dark discharge characteristics of the ultraviolet detection discharge tubes, it is possible to detect a failure due to damage to both of the discharge tubes.

(3) It is possible to provide a highly reliable disaster detection device that does not issue false alarms.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the photodetecting device according to the present invention, and FIGS. 2, 3, 4, and 5 are time charts of the device according to the present invention, respectively. FIG. 6 is a block diagram of the conventional device, and FIG. 7 is a time chart of the conventional device. (1) (la) (lb)...ultraviolet detection discharge tube,
(2)...DC power supply circuit, (3)...Retrigger multivibrator, (4)...Counter, (5)...
Selection switch circuit, (6)...output circuit, (7)...
・Resistance, (8a) (8b) "'Power supply circuit, (9a)
(9b)...transistor, (10a) (10b)
-Transformer, (lla) (12b)... Rectifier diode, (13)... Oscillator, (14)... Fire signal detection section, (,15)... Failure detection section, (16)...・
First OR gate, (17)... Fire detection signal output terminal, (18)... First failure detection section, (19)...
Second failure detection unit, (20)...up/down counter, (21)...first timer, (22)...flip-flop circuit, (23)...second timer,
(24)...Nant gate, (25) second OR gate, (26)...second flip-flop circuit,
(27)... Failure detection signal output terminal, (28)...
Reset signal input terminal. (f) Home appliance tube (+b) Coordinator R Luss diagram diagram diagram diagram (q) = Todoroki---Ya---■ Discharge tube (9) Adjustment diagram diagram discharge 1 lesson +a)澾 (8Ki Eiden) Figure Figure Figure

Claims (5)

[Claims] (1) In a photodetecting device in which a pair of ultraviolet detection discharge tubes are shifted by half a cycle to alternately discharge, the number of pulses accompanying the discharge of each ultraviolet detection discharge tube is compared at regular intervals, and the number of pulses between the two is compared at regular intervals. A photodetecting device comprising a first failure detection section that outputs an output when the difference is greater than or equal to a predetermined value. (2) The first failure detection unit includes an up-down counter that inputs one of the output pulses of the ultraviolet detection discharge tube to the up side and the other to the down side, and detects the difference between the two up-down counters. The photodetecting device according to claim 1, further comprising a timer for presetting to a predetermined value at regular intervals. (3) The photodetection device according to claim (1), further comprising a second failure detection section that outputs an output when the number of pulses associated with the discharge of the pair of ultraviolet detection discharge tubes does not exist at all within a predetermined time. (4) The second fault detection unit includes a counter that measures the output pulses of a pair of ultraviolet detection discharge tubes, a timer that resets this counter at regular intervals, and a counter that outputs no output within the set time of this timer. 4. The photodetecting device according to claim 3, further comprising a gate circuit that outputs an output when there is no signal. (5) The light detection device according to claim (3), wherein the failure signal is outputted based on the OR output of the output signals of the first and second failure detection sections, and the output of the fire detection signal is cut off.